Various types of eco-friendly vehicles are being developed and an electric vehicle is given attention as the eco-friendly vehicle.
Since the electric vehicle is driven using charge/discharge energy of a battery pack, the electric vehicle is well received by consumers in terms of the capability of excellent fuel efficiency and reduced pollutants compared to an engine vehicle. Thus, a battery, which is a core part of the electric vehicle, is the subject of interest and study.
Accordingly, safety of the battery becomes more important as products using the battery increase. Moreover, since the electric vehicle has a structure in which one pack includes a plurality of battery cells as secondary cells and one high capacity battery includes a plurality of packs, the battery of the electric vehicle needs to be more safely maintained than that of a typical portable electric product.
In particular, resistance is caused by aging of the battery cells constituting the battery or by the release of a bus bar for connection between the battery cells. Once such resistance increases, heat may be generated in the battery to thereby damage an internal circuit of the battery or the battery itself. Furthermore, this may cause a battery explosion resulting in a fire.
Accordingly, a technique for diagnosing failure of the battery is needed. In the technique, failure of the battery is generally diagnosed using only a voltage deviation between the battery cells. Particularly, a detection condition is set as wide as possible in consideration of unfavorable circumstances for prevention of misdetection. As a result, an abnormality of a sensing circuit may be detected rather than detection of a battery cell defect and thus a defect diagnosis may be impossible.
Moreover, since the voltage deviation is typically generated within 1V, when a field claim occurs due to a battery cell defect, a DTC (Diagnostic Trouble Code) related to the same may not be operated.
In addition, even when the battery cells are normal, the voltage deviation between the battery cells may be increased when the high-voltage battery is overused. Thus, when the cell voltage by the voltage deviation reaches a given lower limit voltage, usable power of the battery during discharge thereof is limited, resulting in effect on the performance of the vehicle.